In all the job interviews I have done in my decades of work, no-one has ever referred to me by my pronouns.
Furthermore, this information, that refers to your protected characteristics, should not be linked to your job/ volunteer application (except in specific circumstances) as it can lead to candidates being discriminated against, such as for being female. So they really shouldn't be asking for pronouns at this stage so that they 'know how to refer to you.'
Furthermore, I have never seen a form asking me to explain why I don't want to state, say, my ethnicity or sexuality. Its highly inappropriate for them to ask this. This information is for equality monitoring purposes only.
And finally, we all know this creates a hostile environment for people with GC views, especially the ' why not' question. Asking for pronouns is not a neutral act, its a political one.